1. Technical Field
The present invention relates to a plant with piping mounted on branch pipe and boiling water reactor plant.
2. Background Art
In the boiling water reactor plant (hereinafter referred to as BWR plant) having the boiling water reactor (hereinafter referred to as BWR) being a nuclear reactor, case examples have been reported in which an increase in fluctuation pressure accompanying an increase in main steam flow rate occurs when capacity of electric power generation is increased, resulting in damage to equipment in the BWR plant. Countermeasures such as optimizing passage geometry and increasing structural strength for the main steam system have been taken to avoid damaging the equipment. Such case examples and countermeasures are disclosed in G. Deboo, et al., “Quad cities unit 2 main steam line acoustic source identification and load reduction”, ICONE 14, (2006).
Acoustic resonance is thought to be a cause of the fluctuation pressure in the main steam system such as the main steam pipe. In the main steam system from a steam dome in a reactor pressure vessel to a high-pressure turbine via the main steam pipe, pressure waves due to the fluctuation pressure of the steam occur, propagate, and reflect. In consequence, standing waves with a large amplitude (acoustic resonance mode) may be formed and there is a possibility that the amplitude of the fluctuation pressure is increased. In particular, the BWR plants with increased capacity of the electric power generation tend to cause the acoustic resonance because of the large fluctuation pressure of the steam accompanying the increase in the main steam flow rate.
As for the method for suppressing the acoustic resonance, Japanese Patent Laid-open No. 2006-153869, for example, discloses a method for suppressing the fluctuation pressure accompanying the acoustic resonance occurring in the main steam system of the BWR plant by use of a Helmholtz resonance tube. Japanese Patent Laid-open No. 2008-14458 discloses a method for suppressing fluctuation pressure accompanying the acoustic resonance by fitting a canopy member to a cavity where the acoustic resonance is thought to occur.